1. Field of the Invention
The present invention relates to a medical pump driving device and, more particularly to a medical pump driving device having a function of setting the number of rotations of the medical pump, and display means for displaying the set value of the number of rotations. The present invention also relates to a medical pump driving device which removes bubble existing in a liquid channel including a medical pump and the other medical devices. Further, the present invention also relates a medical pump driving device having a sensor unit for obtaining flow rates of liquids such as blood.
2. Description of the Related Art
Generally, in an external circulation using a medical device for artificial lungs and the like or an auxiliary circulation, a medical pump such as a centrifugal pump is used as means for transferring liquid such as blood or Ringer's solution.
In case that liquid is transferred to a human body by the medical pump, the number of rotations of the pump is set in advance before a beginning of the pump driving. Since liquid flow rate is substantially proportional to the number of rotations of the pump, the number of rotations of the pump is set by rotating a dial on an operation panel. In other words, an operator obtains the number of rotations of the pump corresponding to the liquid flow rate at the time of operation, and adjusts a scale of the dial to the obtained number of rotations of the pump. Normally, by the the operator, the dial is made one rotation or 10 or more rotations for obtaining accuracy.
However, in the conventional pump driving device, the number of rotations i.e. rounds per minute (r.p.m) of pump is not displayed on the panel until the pump is actually driven. Due to this, if the pump driving is begun without preparation, liquid is intensively transferred by depending on the set value (the value of the dial scale corresponding to the predetermined number of rotations of the pump). Particularly, in the external circulation using the artificial lungs, if blood is intensively transferred to the human body, a patient often falls into a dangerous state. Therefore, for safety, the operator once returns the dial to a minimum of the scale, thereafter the pump driving is begun, and the dial is rotated little by little so as to gradually increase the number of rotations of the pump. Then, the scale of the dial is set at the set value, and finally reached to the predetermined number of rotations of the pump.
As mentioned above, in the conventional device, the operator must monitor the dial scale during the operation, the operation is complicated, and an excessive load is forcibly imposed on the operator. Moreover, in case that the centrifugal pump is used and the number of rotations is small, there is danger that blood will flow backward.
There is a case that the medical device for the artificial lungs is connected to the medical pump and the auxiliary circulation is performed. In the auxiliary circulation, if bubble exists in the blood channel, a serious trouble occurs. Particularly, the operation for removing bubble from the blood channel of an external circulation circuit of the artificial circuit is extremely important. This is because a large number of hollow fiber membranes and complex and narrow channels such as a tube and a connector, and the like are provided in the blood channel of the external circulation circuit of the artificial lung.
Due to this, a so-called priming operation is performed before the auxiliary circulation. The priming operation is that the blood channel is filled with Ringer's solution, and that bubble is removed therefrom. In general, in the priming operation, vibration is applied to the blood channel as the pump is driven at a constant speed, thereby removing bubble from the inner wall of the channel.
However, great skill is required to the operator so as to perform such the priming operation. Also, a long period of time is needed to perform the priming time. Therefore, the operator cannot freely leave the operation panel, and the operator's movement is restricted.
In recent years, attention has been paid to EBS circulation is manually performed on the spot in a situation that the external circulation circuit of the artificial lungs must be used in the patient at once. In the auxiliary circulation, blood is bled from a femoral vein of the patient, and passed through the artificial lungs. Thereafter, blood is returned from a femoral artery. However, since the conventional priming operation is complicated and needs much time, this generates a big trouble in performing EBS, which needs emergency. Recently, a centrifugal pump has often been used as a means for externally or auxiliarily circulate liquids such as blood and Ringer's solution into the human body while using medical devices such as an artificial lung. This centrifugal pump is characterized in that the amount of liquid pumped out by the pump changes depending upon after-load and change of pressure in the liquid-circulating channel or circuit. In order to accurately control the amount of liquid circulated responsive to any change in the amount of liquid pumped out by the centrifugal pump, it is necessary to accurately know the flow rate of liquid or blood in the liquid-circulating circuit. A sensor is therefore attached to a liquid- or blood-circulating tube which forms the liquid-circulating circuit to measure the flow rate of the liquid flowing in the circuit.
The flow rate sensor is usually connected to the input section of the pump drive unit and when a detection (or flow velocity) signal is applied to the input section, the flow rate is arithmetically calculated responsive to this applied signal. Electro-magnetic and ultrasonic sensors which use electro-magnetic force and ultrasonic wave can be used as the sensor of this type. In the case of a electromagnetic flow meter (or sensor), however, calibration must be conducted before the flow meter is made operative. Until the flow meter can be made ready for operation, therefore, it takes time and it is also troublesome.
The ultrasonic sensor is therefore usually used to measure the flow rate of a liquid in the liquid-circulating circuit of the medical pump driving device. In the case of the conventional ultrasonic sensor, the flow velocity of the liquid is measured and this flow velocity thus measured is converted into the flow rate. When liquid or blood is to be externally or auxiliarily circulated into the human body through the liquid-circulating circuit or channel, therefore, data relating to the inner diameter of the liquid-circulating circuit or tube must be stored, for every sensor, in the memory of a CPU. In addition, flow velocity values measured by sensor units may not be accurate because the sensor units are not necessarily attached to the liquid-circulating tube in same manner. In order to correct these irregular measured flow velocity values, an identifying number must be inputted into the CPU every time a sensor unit is exchanged with another one. This is time consuming and troublesome.